Synchronous machine

ABSTRACT

The present invention concerns a synchronous machine with preferably salient poles with pole windings which are galvanically connected together. The invention further concerns a wind power installation and a method of monitoring a synchronous machine of a wind power installation. The object of the invention is to develop a synchronous machine and a method of operating a synchronous machine, such that the risk of a fire is reduced. A synchronous machine comprising a rotor which has a plurality of poles which are each provided with at least one respective pole winding, wherein the pole windings of a plurality of poles are galvanically connected together by means of a first conductor through which an exciter current flows, characterized in that laid substantially parallel to the first conductor is a monitoring conductor which is acted upon or which can be acted upon with a predeterminable signal, that the monitoring conductor is coupled or connected to a device for detecting the signal and that upon an interruption in the first conductor same is or can be detected by a signal variation in the monitoring conductor and the device for detecting the signal is coupled to a control device which then at least reduces and preferably switches off the exciter current through the first conductor.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of and claims priority under 35U.S.C. §120 from International Application Serial No. PCT/EP02/06182,filed on Jun. 6, 2002 and designating the United States, which claimspriority from German Application Serial Nos. 101 29 365.8 filed Jun. 20,2001 and 101 37 269.8 filed Jul. 31, 2001, both of which areincorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns a synchronous machine with preferablysalient poles with pole windings which are galvanically connectedtogether. The invention further concerns a wind power installation and amethod of monitoring a synchronous machine of a wind power installation.

2. Description of the Related Art

Synchronous machines are generally known. One type of structure isforming either the rotor or the stator with (salient) poles, each polehaving at least one pole winding through which an exciter current flows.That exciter current is always a direct current in synchronous machines.

In that respect the pole windings of all or a plurality of theindividual salient poles are galvanically connected together. As howeverthe pole windings are individually produced and fitted, that connectionis implemented by suitable connecting means such as clamps, solderconnections and so forth. In particular those connecting locations butalso other locations at which for example the winding wire is damagedare subject to the risk of interrupting the galvanic connection, forexample as a consequence of vibration in operation of the machine.

At that interruption, as a consequence of the high current strength, anarc can be formed, which increases the interruption by virtue of theremoval of material and which thus itself also becomes greater and canbecome several centimeters long. In that respect there is the risk thatmaterial in the surroundings ignites and thus a fire occurs whichdestroys the machine.

BRIEF SUMMARY OF THE INVENTION

According to principles of the present invention, one object of theinvention is to develop a synchronous machine and a method of operatinga synchronous machine, such that the risk of a fire is reduced.

The galvanic connection of at least one of the pole windings ismonitored and the exciter current is at least reduced upon aninterruption in the galvanic connection. An interruption can berecognized in good time by virtue of monitoring of the galvanicconnection. The reduction in the exciter current then prevents theproduction of an arc so that the risk of material in the surroundingscatching fire is effectively reduced.

In a preferred embodiment of the invention the exciter current iscompletely switched off in order to be certain of extinguishing an arcwhich is possibly in existence. In that way, upon recognition of aninterruption in good time, it is possible to reliably preclude theinitiation of a fire by an arc.

In a particularly preferred development of the invention, for example inthe case of groups of pole windings which are connected in parallel,only that group in which the interruption has occurred is switched off.That operating procedure provides that only the pole windings of thatgroup are no longer supplied with current, but exciter current stillflows through the other groups so that the synchronous machine cancontinue to operate.

In order to be able to recognize an interruption and in particular anarc in a simple fashion, a conductor which is closely adjacent to thegalvanic connection is acted upon by a predeterminable signal and thepresence of the signal is monitored. If an arc is produced, the adjacentconductor is also interrupted by that arc. In that way the signal isinterrupted and the synchronous machine can be suitably controlled inaccordance with the method of the invention.

In order for the mechanical structure to be of the simplest possibledesign configuration, it is possible to provide a conductor (monitoringconductor) which extends parallel to or in a helical configurationaround the galvanic connection or which is wound around the galvanicconnection or is mounted or glued thereto.

In a particularly preferred embodiment of the invention the monitoringconductor is an electrical conductor, for example a conventionalinsulated copper wire. This is inexpensively available and can bemounted in a simple fashion in accordance with the invention. Inaddition, when using an electrical conductor, it is possible for apredeterminable signal to be introduced, with a low degree ofcomplication and expenditure. In an alternative embodiment themonitoring conductor is an optical conductor. In that case admittedlysupplying the conductor with signals involves a higher degree ofcomplication, but on the other hand the signals are insensitive inrelation to electromagnetic influences and thus have a higher degree offreedom from interference.

In order to enhance the operational reliability of the method accordingto the invention and the synchronous machine, in particular a firstapparatus for supplying the monitoring conductor with a signal and asecond apparatus for monitoring the signal can be redundantly provided.In that way in the event of failure of a component the function thereofcan be taken over by a redundantly present component.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

The invention is described in greater detail hereinafter with referenceto the Figures in which:

FIG. 1 shows a sector-shaped portion of a pole wheel,

FIG. 2 shows a view on an enlarged scale of detail from FIG. 1,

FIG. 3 shows a simplified view of a conductor in a first embodiment ofthe invention with an electrical conductor,

FIG. 4 shows an alternative embodiment of a monitoring system with anoptical conductor,

FIG. 5 shows a monitoring system without an additional conductor, and

FIG. 6 shows a view of a wind power installation with a current bus bararound which is wound a fuse wire.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a simplified view showing a section of a pole wheel of asynchronous machine such as a generator. Reference 10 denotes theindividual pole pieces of the salient poles while reference 12 denotesthe pole windings arranged on the salient poles.

Those pole windings 12 are connected together by a galvanic connection14 so that the pole windings 12 are connected in series and thus allhave the same current flowing therethrough. As the pole windings 12 aremanufactured individually, the connections are connected together forexample by connecting sleeves 16.

FIG. 2 is a detail view on an enlarged scale from FIG. 1 and shows twopole pieces 10 with pole windings 12 arranged therebehind. Between thepole windings 12 there is a galvanic connection 14. That connection ismade by the conductor 14 from which the pole winding 12 is wound beingconnected at a connecting location 16, for example with a connectingsleeve 16 or by a solder connection or by another suitable connection,to the conductor of the adjacent pole winding 12. Connecting locations16 of that kind are also to be found in turn between the two polewindings 12 illustrated in this Figure and their respective adjacent(but not illustrated) pole windings 12. In particular however thoseconnecting locations 16 are structural weak points in that galvanicconnection 14 so that an interruption can occur there for example as aconsequence of the vibration which occurs in operation of thesynchronous machine.

Illustrated around the galvanic connection 14 and the connectinglocation 16 is a conductor 18 which is wound in a helical configuration,acting as a monitoring device or monitoring conductor.

If an interruption occurs for example due to vibration at the connectinglocation 16, an arc is formed there because the interruption isinitially very small and the exciter current is relatively high.Material is removed by the arc and that causes the interruption to beincreased in size. That removal of material by the arc however alsointerrupts the conductor 18 so that such interruption is detected byvirtue of suitable monitoring of the conductor 18 and it is thuspossible to conclude that the galvanic connection 14 is now interruptedand an arc has been formed. Thereupon it is possible to take suitablemeasures such as switching off the exciter current in order toextinguish the arc and thus to prevent the occurrence of a fire.

FIG. 3 is a view showing in simplified fashion a possible way ofmonitoring the situation with a conductor 18. The conductor 18 is atground potential at one side. Provided at the other side of theconductor is a switching device 20, in this case a relay, which issupplied with a sufficient voltage so that it can pull up. That relayhas an opening device 22 which is thus opened when the relay 20 isoperated. If now an interruption in the conductor 18 occurs, the relay20 is released and the opening device 22 closes. That closing action canbe detected for example at the connecting terminals 24 by adownstream-connected device, and suitably evaluated.

It will be appreciated that the relay can also be arranged at the otherside of the conductor 18. Then the conductor is supplied with a suitablevoltage which causes the relay 20 to operate and in this case also therelay 20 is naturally released as soon as the conductor 18 isinterrupted, which can lead directly to the exciter current beingswitched off.

FIG. 4 shows an alternative embodiment of the monitoring systemillustrated in FIG. 3. The conductor 18 in FIG. 4 is a light waveconductor or optical fiber. An optical signal is coupled into the lightwave conductor 18 by a light source 30, here illustrated in the form ofa light emitting diode. At the other end, the optical signal is receivedby a receiver 32, in the present case a photoresistor, which in turn canbe a component part of a bridge circuit.

Therefore as long as the light emitted by the light source 30 istransmitted through the conductor 18, the receiver 32 is of a givenresistance. If there is an interruption in the conductor 18, then thelight which is introduced from the light source 30 no longer reaches thereceiver 32, the receiver 32 experiences a change in its resistance, andin that way the interruption in the conductor 18 can be recognized.

It will be appreciated that the receiver can also be for example in theform of a phototransistor or any other light-sensitive element.

An alternative form of the system for monitoring the galvanic conductor14 is shown in FIG. 5. In this case, at a coupling-in point 36, inaddition to the flowing exciter current, an ac voltage of smallamplitude and predetermined frequency is superimposed. That ac voltageis monitored at the coupling-out point 38. In this respect coupling-outcan be effected for example capacitively or inductively. In that respectthe Figure shows a plate 40 of a capacitor. The other plate can beformed for example by the galvanic connection 14 itself.

Once again the ac voltage which is coupled out by the capacitor 40 canbe monitored by a suitable, downstream-connected circuit. If aninterruption in the galvanic connection 14 occurs, the exciter currentis admittedly still transported by the arc but the superimposed acvoltage is no longer so transported so that it can also no longer becoupled out at the coupling-out point 38. That makes it possible todetect the interruption in the galvanic connection 14.

If a plurality of pole windings are brought together to constitute agroup and there are a plurality of groups of such pole windings, it isappropriate, for each group, to include its own specifically providedfuse wire so that, upon an interruption in the fuse wire, only theexciter current of the affected group is reduced or switched off so thatthe other groups can continue to be operated as usual in order to permitthe generator to continue to operate.

If therefore each pole winding group has its own conductor 18, which isacting as a fuse wire, with the appropriate feed-in and monitoringdevice, that affords a clear association in respect of the pole windinggroup and the respective conductor 18 and actuation of the pole windinggroup can be suitably interrupted when the conductor 18 is severed. Afurther possible option involves using an individual conductor 18 forthe pole winding of the entire pole wheel and switching off the excitercurrent in the case of an interruption in the fuse wire. When thatinterruption which must be maintained for a predetermined period of timein order to be certain of extinguishing the arc is reversed again, asuitable exciter current can flow again. Then only the pole windinggroup in which the interruption occurred is excluded therefrom. Thisarrangement however suffers from the disadvantage under somecircumstances that the conductor 18 is then interrupted so that eitherthe operation has to be continued without the conductor 18 or it cannotbe continued for reasons of operational safety.

FIG. 6 illustrates that the invention is not limited for example just tomonitoring the generator of the wind power installation, but can also beapplied to other parts of the wind power installation. Thus for examplethe problem of arc formation occurs not only upon an interruption in thepole windings, but can also occur upon an interruption in the directcurrent bus bars 62 with which the electrical energy generated by thegenerator is passed from the machine pod 64 to the power switchboardcabinets which are usually arranged at the base of the pylon 66 oroutside the pylon. The current bars 62 in the illustrated example serveas usual to pass the electrical power from the generator in the pod 64of the wind power installation to the base of the pylon or theelectrical devices disposed there such as inverters and/or transformers70. Those direct current bus bars 62 usually consist of a metal, forexample aluminum, and are fixed at the interior of the pylon 66 to thewall thereof and taken downwardly therein. As the pylon 66 also moves byvirtue of the overall wind loading on the wind power installation (inthe region of the pod 64 that movement can easily be of an amplitude inthe range of between 0.5 m and 2 m), the current bus bars 62 are alsocorrespondingly moved and loaded, which in the worst-case scenario, ifthe movements were too great or if the current bus bars 62 were notcleanly routed, can result in an interruption in the current bus bars62, whereby an arc can also be formed between the separated parts and asvery high flows of energy are to be found at that location, that canlead to very severe damage to the wind power installation, especially asit is also certainly possible for the arc which is produced to jump backto the grounded pylon 66 so that the outbreak of a fire also cannot beexcluded.

The structure illustrated in FIG. 6 shows a view illustrating part of athree-wire current bus bar 62 being wrapped with a conductor 18, actingas a fuse wire, in which respect it is possible to use the monitoringdevices shown in FIGS. 3 through 5 for monitoring the fuse wire. If theinterruption occurs in a current bus bar, that also results in aninterruption in the conductor 18 and in such a case the entireinstallation is shut down and is not further operated, forself-protection purposes, especially as in any case then the current busbars 62 must not only be repaired but under certain circumstances alsohave to be replaced in order to guarantee reliable continuation ofoperation thereafter.

All of the above U.S. patents, U.S. patent application publications,U.S. patent applications, foreign patents, foreign patent applicationsand non-patent publications referred to in this specification and/orlisted in the Application Data Sheet, are incorporated herein byreference, in their entirety.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A synchronous machine comprising: a rotor which has a plurality ofpoles which are each provided with at least one respective pole winding,wherein the pole windings of a plurality of poles are galvanicallyconnected together by means of a first conductor through which anexciter current flows; a monitoring conductor which can be acted uponwith a signal, being positioned substantially parallel to the firstconductor the monitoring conductor being coupled to a device fordetecting the signal such that an interruption in the first conductorcan be detected by a signal variation in the monitoring conductor; and adevice for detecting the signal that is coupled to a control devicewhich then reduces the exciter current through the first conductor, thedevice for acting upon the monitoring conductor with a signal being of aredundant design that includes a first and a second device for actingupon the monitoring conductor with a signal.
 2. A synchronous machineaccording to claim 1 characterized by a monitoring conductor extendingin a helical configuration around the galvanic connection.
 3. Asynchronous machine according to claim 1 characterized in that themonitoring conductor is in the form of an electrical conductor.
 4. Asynchronous machine according to claim 1 characterized in that themonitoring conductor is in the form of an optical conductor.
 5. Asynchronous machine according to claim 1 characterized in that the firstand second devices for acting upon the monitoring conductor with asignal form a structural unit.
 6. A wind power installation having asynchronous machine according to claim
 1. 7. A method of monitoring theoperation of a synchronous machine which has a rotor which comprises aplurality of parallel-connected groups of poles with a pole winding,wherein the pole windings of a plurality of poles are galvanicallyconnected together and an exciter current flows through the polewindings, wherein there are provided means for monitoring the galvanicconnection of the pole windings and upon an interruption in the galvanicconnection the exciter current is switched off in the group of polewindings with the galvanic interruption but is maintained in othergroups.
 8. A method according to claim 7 characterized in that torecognize the galvanic interruption an ac voltage of predeterminablefrequency and/or amplitude is superimposed on the exciter current at atleast one predeterminable first position of the galvanic connection andthe presence of said ac voltage is monitored at at least one secondpredetermined position by means of a suitable monitoring device.
 9. Amethod according to claim 7 characterized in that to recognize agalvanic interruption a monitoring conductor closely adjacent to thegalvanic connection is acted upon by a predeterminable signal and thepresence of the predetermined signal is monitored and upon failure or alarge change in the predetermined signal a control device is caused toreduce and/or entirely switch off the exciter current.
 10. The methodaccording to claim 7 in which the exciter current is switched off.
 11. Awind power installation comprising: a rotor; a generator coupled theretoand which in operation of the wind power installation produceselectrical power which is passed by means of current bus bars from thegenerator from the region of the pod to the base region of the pylon andis there processed for being fed into a power supply network; amonitoring conductor positioned substantially parallel to the bus barwhich can be acted upon by a predeterminable signal, wherein themonitoring conductor is coupled to a device for detecting the signal andthat upon an interruption in the bus bar that interruption can bedetected by a signal change in the monitoring conductor and the devicefor detecting the signal is coupled to a control device which thenreduces the current through said bus bar.
 12. A wind power installationaccording to claim 11 characterized in that the monitoring conductor iswound around an individual current bus bar or a group of current busbars and extends parallel and substantially from the beginning to theend of the current bus bar.